Vitreous fluorophotometry (VFP) is a clinical procedure for measuring the spatial distribution of fluorescence along the optical axis in a human subject's vitreous following administration of a fluorescent dye. In this project the clinical instrument is a Fluorotron Master manufactured by Coherent, Palo Alto, CA, and the dye is sodium fluorotron given by intravenous injection. The purpose of the project is to improve the protocols for conducting the measurements, processing the output from the instrument and analyzing the results from the population of normal volunteers and patients. One disease to be considered is diabetes and the associated pathology diabetic retinopathy. The goals are to evaluate the procedure for use in (1) screening for early detection, and (2) monitoring for treatment efficacy. A pharmacokinetic mathematical model has been developed which describes the rate of appearance of fluorescein in the vitreous in terms of the blood-retinal barrier permeability (characterized by permeability coefficients of the retina-vitreous interface) and transport of fluorescein within the vitreous by diffusion (characterized by a diffusion coefficient). Plasma protein binding of fluorescein is also incorporated. measurements have been made on 22 normal volunteers to evaluate the performace of the instrument, establish baseline parameter ranges, and critique existing protocols/analysis schemes.